Homopolar dynamo-electric machine



April 20, 1937. P. l. cHANDEYssoN 2,077,742

HOMOPOLAR DYNAMO-ELECTRIC MACHINE Original Filed July 14. 1953 Patented Apr. 20, 1937 UNITED STATEEi PATE-Nr orifice Application July 14, 1933, Serial No. 680,338 Renewed October 21, 1935 S Claims.

This invention pertains to dynamo-electric machines of the homopolar type.

One of the objects of this invention is to provide a field structure for such a machine of the .simplest type.

Another object is to provide a structure which will permit free access to the brushes.

Another object is to provide a simple field circuit and an exciting coil therefor mounted in a simple and convenient manner.

A further object is to provide means for cooling the exciting coil.

Further objects will appear from the following description taken in connection with the accompanying drawing, in which:

Figure 1 is a side View of a machine embodying this invention, and

Figure 2 is a section on line Z-2 of Figure l.

Referring to the drawing, I designates frame members on which are mounted bearings 2 in which a rotor 3 is journalled. This rotor is preferably constructed of a single cylindrical piece of steel of the proper diameter. It may be provided with a peripheral coating of copper or other highly yconducting material adapted to carry currents generated in the rotor. The eld structure comprises a yoke member 4 which also in the embodiment illustrated provides a base for a plurality of core elements 5 and 6. The middle element 5 is usually about twice the cross section 0f one of the end elements 6 as it is required to carry twice the amount of magnetic iiux. Each of the elements 5 and 5 is provided with a bore l, the bores of all three core elements being in alinement so that the rotor 3 may traverse all of these bores.

It will be noted that this arrangement provides a magnetic circuit in which the magnetic ux may pass upwardly through the middle core element 5, and, crossing the air gap between this element and the rotor, enter the rotor dividing after entry to pass in both directions along the rotor. Each branch of the ux travels toward one end of the rotor and passes outwardly again across the air gap between the rotor and the end element 6. Here the flux passes downwardly along the 'element 6 and returns to the middle element through the yoke 4. Thus a magnetic circuit is provided which has two paths in which the ux circulates in opposite directions. The actual direction of positive flux may, of course. be either up or down in the middle core element 5, the up direction being chosen for illustration only and the magnetic circulation being indicated by the dotted lines in Figures 1 and 2.

When the rotor 3 is driven in rotation by any suitable means, such for instance as a driving connection to the gear 8 an electromotive force will be generated in the rotor acting longitudinally thereof in that portion opposite the core element 5. The direction of this E. M. F. will, of course, depend upon the direction of the magnetic eld and also on the direction of rotation of the rotor. In order to collect current from the rotor brushes 9 may be mounted in any suitable manner to bear on the surface of the rotor in the spaces between the middle and end core elements 5 and ii. Conductors IG and Il may then carry the collected currents to external circuits.

It has been found that the proportions of the core elements 5 and 6 have a denite relation to the efficiency of operation of the machine. The

most satisfactory performance is obtained when these proportions are such that the magneticv density in the air gap is substantially uniform throughout the circumference thereof. It has been found, further, that such a result may be obtained when the axial length of the middle core element 5 is substantially equal to the rotor diameter, the transverse width of the core elements is twice this amount, while the height of the top of the core elements above the top of the rotor is one-eighth of the rotor diameter. axial length of the end elements 6 is, of course, about half that of the middle element 5.

It will be noted that the arrangement of the core elements 5 and 5 together with the yoke Il provides an E-shape field structure providing suitable capacity for carrying the magnetic uX and also a simple mechanical arrangement. The bore l' or each core element being placed near the top of that element places the rotor in an exposed position. Accordingly the brushes 9 are located in a position where they are freely accessible from all sides. The iield structure is open laterally and at the top so as to permit such free access to the brushes. 1t is a great advantage in a machine oi this type to provide for free accessibility to the brush rigging since practically the only part of the machine which is subjected to wear and which may require occasional attention is the brushes. With the structure described brushes may be replaced during the operation of the machine in a simple and convenient manner.

In order to provide excitation for this machine a eld exciting coil I2 is provided. This coil is placed about the middle core element 5 and the general structure of the eld frame is such that this is a convenient and practical location for this The.

coil. In order to provide for cooling the coil l2 a container I3 may be provided surrounding the core element and adapted to contain oil or other cooling medium in which the coil may be immersed. The arrangement of the yoke 4 to provide a base for the machine is such as to make it convenient to support the container I3 directly on the base as indicated in the drawing.

It will be seen, therefore, that this invention provides a homopolar machine of the simplest construction. The simplicity of the E-Shaped field structure renders it simple to manufacture and also provides an open frame unobstructed laterally so that free access to the brushes from all sides is provided. Such a machine, of course, may be operated as either a generator 0r a motor and in either case a compact and simple structure is provided.

While, of course, this machine has been described as a unitary structure it will be obvious that individual features or sub-combinations thereof may be used without reference to other parts or the complete combination and the ernployment of such individual features or sub-combinations is contemplated by this invention and Within the scope of the appended claims. It is obvious that various changes may be made, within the scope of the appended claims, in the details of construction without departing from the spirit of this invention; it is to be understood, therefore, that this invention is not limited to the specic details shown and/or described.

Having thus described the invention, what is claimed is:

1. In a homopolar dynamo-electric machine, a yoke and a plurality of core elements comprising an E-shaped field structure, said core elements having axially alined bores, a cylindrical rotor of substantially uniform diameter traversing said bores and mounted for rotation therein, and

brushes mounted for sliding Contact with the cylindrical surface of said rotor in the spaces between said core elements, said eld structure being open laterally to provide free access to said brushes.

2. In a homopolar dynamo-electric machine, a yoke and a plurality of core elements comprising an E-shaped lield structure, said core elements having axially alined bores, an exciting coil on one of said core elements, a rotor traversing said bores and mounted for rotation therein, and means for cooling said coil.

3. In a homopolar dynamo-electric machine, a yoke and a plurality of core elements comprising an E-shaped iield structure, said core elements having axially alined bores, an exciting coil on one of said core elements, a rotor traversing said bores and mounted for rotation therein, and a container surrounding said last core element to receive said coil adapted to contain cooling uid.

4. In a homopolar dynamo-electric machine, a yoke and middle and end core elements comprising an E-shaped field structure, said core elements having axially alined bores, a cylindrical rotor of substantially uniform diameter traversing said bores and mounted for rotation therein; said end core elements each having substantially onehalf of the area of cross section of the magnetic path therethrough of that of said middle section, and said middle section having an axial extent substantially equal to said rotor diameter; and brushes mounted for sliding Contact with the cylindrical surface of said rotor in the spaces between said core elements, said field structure being laterally open to provide free access to said brushes all round the rotor.

5. In a homopolar dynamo-electric machine, a yoke and middle and end core elements comprising an E-shaped iield structure, said core elements having axially alined bores, a cylindrical rotor of substantially uniform diameter traversing said bores and mounted for rotation therein; said end core elements each having substantially one-half of the area of cross section of the magnetic path therethrough of that of said middle section, and said middle section having an axial extent substantially equal to said rotor diameter; the transverse extent of said core elements being substantially equal to twice the rotor diameter, and the depth of each of said core elements over the top of the rotor being substantially equal to one-eighth of the rotor diameter; and brushes mounted for sliding contact with the cylindrical surface of said rotor in the spaces between said core elements, said field structure being laterally open to provide free access to said brushes all round the rotor.

6. In a homopolar dynamo-electric machine, in combination with a cylindrical rotor, a plurality of core elements spaced along said rotor and having alined bores traversed thereby, a yoke providing with said rotor and said core elements a magnetic circuit, one of said core elements being formed with respect to said rotor tapering in cross-section outwardly beyond said rotor adapted by its varying reluctance so provided to distribute the magnetic flux substantially uniformly throughout the air gap between said rotor and said element, and current collecting means engaging said rotor in the space between said core elements.

'7. In a homopolar dynamo-electric machine, in combination with a cylindrical rotor, a plurality of core elements spaced along said rotor and having alined bores traversed thereby, a yoke providing with said rotor and said core elements a magnetic circuit, said core elements being formed to present to the ux in said circuit a circumferentially varying cross-section providing a progressively increasing reluctance in the outer portion of said circuit in order to distribute said flux uniformly throughout the air gap.

8. In a homopolar dynamo-electric machine, a yoke and a plurality of core elements outstanding therefrom and providing therewith an E-shaped eld structure, said core elements having axially alined bores, a cylindrical rotor traversing said bores and mounted for rotation therein, and a plurality of brushes massed about said rotor in the spaces between said elements and bearing upon the cylindrical surface of said rotor for sliding, current collecting engagement therewith.

PIERRE I. CHANDE'YSSON.

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